Chevy Fuel Gauges

[Lowe]

I was talking to a couple guys this morning, and all of us have been having trouble with our fuel gauges on our Chevy's the last month or two. The gauges have been staying on full for a long time, and once it reaches half you only have a few gallons of gas left. Many fuel gauges act this way, but I've never seen them act this extreme and I've never seen them change so abruptly (or at all, I guess). Another guy said his '04 Chevy van started out that way, and now stays on "Full" all the time and he has to be very careful not run out of gas.

Anybody else out there having this problem? I'm guessing it has something to do with the winter blend of gas, maybe making the float stick, but I'm not sure.

[Farley]

My Grandpa has a 99 chev with the exact same problem. It started a few weeks ago. That's strange.

[Gus]

I had the same problem on my 98 Tahoe. First time it did it I was on my way up fishing in the middle of the night and I ran out of gas when the needle said 1/4! I think I toasted the fuel pump then and within a month I couldn't start the truck. Replaced the entire unit which included the fuel gauge sending unit. Never had a problem after that. You are not alone! Something is funny with these chevy's.

My 03 silverado has yet to follow in it's footsteps. I've still got my fingers crossed.

[IFallsRon]

I've read that most of the fuel guage concerns have been caused by an intermittant connection at the fuel sending unit. It seems to be a common problem. There's been a couple service bulletins. You'll have to check if they relate to your models.

[Ruttin' Buck]

This is coming from a guy with an old hunting/fishing/hauling Chev...
'88 to be exact...so maybe not the same thing.

Had s similar thing happen with my truck a few years back. Gauge showed full or occassionally would bounce erratically and end up at full again. Well, the answer is not a short one.

Turns out, Chevy began using a plastic baffle tub that is secured inside the tank. This tub is held down (magically I think) by two non treaded studs and I imagine a few fasteners of some sort. I think someone at the plant 'wishes' it in place.

In any event, when this thing comes loose it gets sloshed back and forth in the tank but the sending unit of the pump gives it something to bang against. Eventually, after it hammers against the fuel gauge float it destroys it. When this happens, you will show full all the time. Soon after it will destroy the filter sock on the pump and eventually the pump will go intermittent or fail completely.

My pump went intermittent (which is actuall odd) and I spent a few hours troubleshooting this. I got to syphon 30 gallons of fuel out of the old girl and pull the tank. Not a bad job, but found out there's no way to get this baffle back in securely through the sending unit hole. I bought a new tank for $80, fuel pump and it was ready to go again.

The fuel gage actually broke so that the finger that runs along a resistance block no longer touched it. 2 cable ties fixed that problem.

To check if the baffle is loose, when you think your at half tank, with truck off, shake the vehicle back and forth to get the gas sloshing. You will be able to hear the baffle 'tapping' around inside the tank.

[Lowe]

My gauge doesn't bounce, neither did the other guys. They just stay above half until the tank is almost dry. I have 98 Silverado, the other guy a '97 Silv, and the other one was the '04 van. All of them started acting up very recently, and it sounds like we're not the only ones to have this problem in the past month or two.

If it was bouncing I could see the sensor/float being stuck on something or broke, but this seems like something different.

[andy j]

IFALLSRON,
wher do i find these service bulletins?

[IFallsRon]

Check with your garage guy or the dealership. You can search alldata.com to see if there's a specific bulletin on your vehicle. You can refer to that number when you call the dealership, too.

Here's typical info for a 98 Tahoe: 83-83-07 MAR 98 Fuel Level Sensor - Replacement Procedure

[Ruttin' Buck]

I just had noticed andy j said his bounced a bit. Mine for the most part always stayed in one spot...oftentimes full. But occassionally when being rattled, it would touch off on the resistance block and the gage would bounce.

To get a bit more into the technical angle. I was going with the large difference in coefficients of thermal expansion between plastic and steel. Plastic has a higher coefficient, by 6-8x depeding on the plastic used! So very cold conditions would mean that the plastic baffle would linearly 'contract' 6-8 times more than the steel post it is fastened onto. This can result in the pre-load of the fastener being lost and subsequently the baffle coming loose.

The most common condition between all of you having problems would likely be the fact that all of the vehicles just experience a few months with temps below 0 at times.

Doesn't cost anything to give your truck a shake!

my.02

[Ruttin' Buck]

One thing I forgot to mention. The baffle tub is quite small. So it is possible that it may be out of place but has not destroyed your fuel gage. If it is out of place it is quite likely that the float could end up resting on the top of the baffle tub. This would prevent it from ever getting below say 1/4-1/2 full.

If the gage read full all the time, it's getting no signal. Whether it be from where the gage is mounted to the sending unit or at the connection outside the tank is anybody's guess!

[Lowe]

Thanks for the info, Buckblaster, that makes sense. I'll give her a shake when it goes down a little. I did notice my fuel pump was pretty loud a while back during a cold spell. I tossed some heat in the tank, since I figured there was a little bit of ice in the fuel filter, now I'm beginning to wonder if it wasn't something else.

[andy j]

I have a 99 chevy and the gauge doesn't even work anymore, it flips from empty to full all the time.